Neisseria gonorrhoeae is an evolving species of bacteria. Strains isolated in 1935-1945 from patients with gonorrhea have relatively few nutritional requirements in comparison to recent isolates. We are investigating the biosynthetic defects of the arginine and pyrimidine pathways and are transferring the mutant auxotrophic markers into the uniform background of a gonococcal strain isolated in 1943. We will examine the linkage relations between various gene loci represented in this isogenic set of strains.